1. In some protostomes, the embryonic blastocoele persists as a body cavity. 2. A blastula is a sphere of cells surrounding a blastocoele . 3. The blastocoele also allows blastomeres to move during the process of gastrulation. 4. In mouse embryo, blastocoele formation begins at the 32-cell stage. 5. The blastula stage of early embryo development begins with the appearance of the blastocoele . 6. The animal cap forms the roof of the blastocoele and goes on primarily to form ectodermal derivatives. 7. This layer surrounds the inner cell mass and a fluid-filled cavity known as the blastocoele . 8. From the stage of having 128 cells, the embryo develops a cavity, the blastocoele , and is called a blastula. 9. During this process, water enters the embryo, aided by an osmotic gradient which is the result of epithelial cells that line the blastocoele . 10. A common feature of a vertebrate blastula is that it consists of a layer of blastomeres, known as the blastoderm, which surrounds the blastocoele .
